We have a 10:25 reservation next month, so I know it's at least that late. For us that's going to be a sleep in morning and we'll just Uber/Lyft over to AKL from WL, then take the bus to AK (park) after our late breakfast. We did this last month and it worked great for us but then we aren't really rope droppers anyway.
I've read that the waits for busses back to resorts from the parks can be long in the morning. They don't necessarily just run back and forth between a certain park and resort. If you want to try going to the park first, I'd recommend using a rideshare to get to Boma if you don't have your own car.